IUP

"IUP is a multi-platform toolkit for building graphical user interfaces. It offers APIs in three basic languages: C, Lua and LED.

Its library contains about 100 functions for creating and manipulating dialogs.

IUP's purpose is to allow a program to run in different systems without changes - the toolkit provides the application portability. Supported systems include: GTK+, Motif and Windows.

IUP uses an abstract layout model based on the boxes-and-glue paradigm from the T_EX text editor. This model, combined with the dialog-specification language (LED) or with the Lua binding (IupLua) makes the dialog creation task more flexible and independent from the graphics system's resolution.

Currently available interface elements can be categorized as follows:

• Primitives (effective user interaction): dialog, label, button, text, multi-line, list, toggle, canvas, frame, image.
• Composition (ways to show the elements): hbox, vbox, zbox, fill.
• Grouping (definition of a common functionality for a group of elements): radio.
• Menu (related both to menu bars and to pop-up menus): menu, submenu, item, separator.
• Additional (elements built outside the main library): dial, gauge, matrix, tabs, valuator, OpenGL canvas, color chooser, color browser.
• Dialogs (useful predefined dialogs): file selection, message, alarm, data input, list selection.

Hence IUP has some advantages over other interface toolkits available:

• Simplicity: due to the small number of functions and to its attribute mechanism, the learning curve for a new user is often faster.
• Portability: the same functions are implemented in each one of the platforms, thus assuring the interface system's portability.
• Customization: the dialog specification language (LED) and the Lua binding (IupLua) are two mechanisms in which it is possible to customize an application for a specific user with a simple-syntax text file.
• Flexibility: its abstract layout mechanism provides flexibility to dialog creation.
• Extensibility: the programmer can create new interface elements as needed.

IUP is free software, can be used for public and commercial applications."

http://webserver2.tecgraf.puc-rio.br/iup/

https://sourceforge.net/projects/imtoolkit/

https://sourceforge.net/projects/canvasdraw/